The present invention belongs to the technical field of a magnetic tape used for DDS (digital data storage), DAT (digital audio tape) and the like. More particularly, the present invention relates to an evaluation reference tape capable of adequately evaluating a sensitivity correction of a dropout testing apparatus and a recording/replaying system of a magnetic tape, a method of manufacturing the evaluation reference tape and an apparatus for manufacturing the evaluation reference tape.
Magnetic tapes used for the DAT or the DDS are basically composed of a base layer which is a film such as PET (polyethylene terephthalate) or the like, a magnetic recording layer formed on one of the surfaces of the base layer, a backing layer formed on the surface of the base layer opposite to the magnetic recording layer for the purposes of improving the stability of the magnetic tape when it is transported and the strength thereof, and the like.
In the magnetic tape having such composition as described above, a defect of the magnetic recording layer derived from a scar or the like will cause a phenomenon such as a decrease of recording magnetic power or output, a recording or replaying error and is commonly called as dropout.
Therefore, in the magnetic tape, it is ideal that there is no dropout, however, the dropout is intrinsically unavoidable in the magnetic tape. For this reason, a dropout testing apparatus is employed at the time of manufacturing the magnetic tape to measure the number of the dropout which has exceeded a predetermined threshold value of at least one of output decrease and time length and, if the thus measured number exceeds, to judge the magnetic tape to be inappropriate or NG (no good) as a product.
In the case of DAT cartridges, there are many cases in which actual drives (recording/replaying apparatuses) are remodeled and then used as the dropout testing apparatuses. The threshold of the number of the dropout differs from tape to tape in accordance with the type thereof.
In order to appropriately execute the above-described dropout testing, it is necessary that the dropout testing apparatus should correctly measure the number of the dropout which exceeds the predetermined value so that sensitivity of the dropout testing apparatus should be appropriately set.
Therefore, in manufacturing of the magnetic tape, the magnetic tape which serves as reference, namely, an evaluation reference tape (hereinafter referred to simply as xe2x80x9creference tapexe2x80x9d) is manufactured so that it is put to use in sensitivity correction (calibration) of the dropout testing apparatus.
On the other hand, such a reference tape is not capable of knowing how large and deep a defect actually is on a magnetic recording layer.
There can only be known how large and deep the defect is by analyzing the magnetic tape. However, since it is essential that such analysis requires observation using an electron microscope or magnetic phenomenon, the thus analyzed magnetic tape results in being destroyed and no more applicable as a reference tape; therefore, such analysis is ordinarily performed on a part of the magnetic tape.
For the above-described reason, at present, sensitivity correction of the dropout testing apparatus can not be performed in accordance with the depth or size of the defect in the reference tape so that, in the dropout testing, correspondence between the dropout and the depth and size of the defect is vague; as a result, good quality control can not be performed.
A first object, therefore, of the present invention is to solve the above-described problems of the conventional technology and to provide an evaluation reference tape capable of performing sensitivity correction of a dropout testing apparatus in accordance with a depth or size of a defect, thereby, performing a more adequate quality control and production control by appropriately comprehending performance of the dropout testing apparatus and performing a dropout testing with higher precision which has taken individual differences and deterioration with age of the dropout testing apparatuses, and evaluating performance of recording/replaying system of the magnetic tape with higher precision and appropriately by measuring the performance of the recording/replaying system quantitatively.
A second object of the prevent invention is also to provide a method of manufacturing the evaluation reference tape which is capable of efficiently manufacturing the above-described evaluation reference tape of the present invention.
A third object of the present invention is further to provide an apparatus for manufacturing the evaluation reference tape which implements the method of manufacturing the evaluation reference tape of the present invention.
The above-described first object of the present invention can be attained by an evaluation reference tape comprising a magnetic tape having a base layer and a magnetic recording layer formed on one of both surfaces of the base layer, and at least one recess formed on the magnetic recording layer by processing the magnetic recording layer.
Preferably, the at least one recess corresponds to a dropout of the magnetic tape.
Preferably, the at least one recess is at least one straight groove extending in a longitudinal direction of the magnetic tape or at least one oblique groove extending in an direction oblique to the longitudinal direction of the magnetic tape.
Preferably, the at least one straight groove and the at least one oblique groove are arranged in at least one row along a widthwise direction of the magnetic tape.
The above-described second object of the present invention can be attained by a method of manufacturing an evaluation reference tape, comprising the steps of allowing at least one of a laser beam in a visible region and a laser beam in an ultraviolet region to be incident on a magnetic recording layer of a magnetic tape while the magnetic tape having a base layer and the magnetic recording layer formed on one of both surfaces of the base layer is transported in a longitudinal direction, and processing the magnetic recording layer to form a recess thereon.
Preferably, the laser beam to be incident on the magnetic recording layer of the magnetic tape is selected from the group consisting of a plurality of laser beams which have been split and imaged by a multiple-lens, a plurality of laser beams formed by splitting a laser beam by a splitting device, a laser beam scanned by a light scanning element, a plurality of laser beams split and imaged by simultaneously using both the splitting device and the multiple-lens.
Preferably, the at least one recess corresponds to a dropout of the magnetic tape.
Preferably, the at least one recess is at least one straight groove extending in a longitudinal direction of the magnetic tape or at least one oblique groove extending in an direction oblique to the longitudinal direction of the magnetic tape.
Preferably, the at least one straight groove and the at least one oblique groove are arranged in at least one row along a widthwise direction of the magnetic tape.
The above-described third object of the present invention can be attained by an apparatus for manufacturing an evaluation reference tape, comprising at least one light source for emitting at least one of a laser beam in a visible region and a laser beam in an ultraviolet region, an optical system which allows the laser beam emitted from the at least one light source to be incident on a predetermined processing position, a transportation device for transporting a magnetic tape having a base layer and a magnetic recording layer formed on one of both surfaces of the base layer in a longitudinal direction with the magnetic recording layer facing upstream of a light path of the laser beam while it is held in registry with the predetermined processing position, and a device for securing flatness of the magnetic tape when it is transported by the transportation device while it is held in registry with the predetermined processing position.